1. Field
The following description relates to acoustic signal processing, and more particularly, to an apparatus and method for enhancing audio quality by alleviating noise using a non-uniform configuration of microphones.
2. Description of the Related Art
As mobile convergence terminals including high-tech medical equipment, such as high precision hearing aids, mobile phones, ultra mobile personal computers (UMPCs), camcorders, etc. have become more prevalent today, the demand for products using a microphone array has increased. A microphone array includes multiple microphones arranged to obtain sound and supplementary features of sound, such as directivity (e.g., the direction of sound or the location of sound sources). Directivity may be used to increase sensitivity to a signal emitted from a sound source located in a predetermined direction by use of the difference between the times of arrival of sound source signals at each of the multiple microphones constituting the microphone array. By obtaining sound source signals using the principal of directivity in a microphone array, a sound source signal input from a predetermined direction may be enhanced or suppressed.
Recent studies have been directed toward: a method of improving a voice call quality and recording quality through directed noise cancellation; a teleconference system and intelligent conference recording system capable of automatically estimating and tracking the location of a speaker; and robot technology for tracking a target sound.
Beamforming algorithm-based noise cancellation is one technique applied to most microphone array algorithms. As an example of the beamforming noise cancellation method, a fixed beamforming technique is used for beamforming that is independent of characteristics of the input signals. According to the fixed beamforming technique, a beam pattern varies depending on the size of a microphone array and the number of elements or microphones included in the microphone array. Desirable beam patterns for lower frequency bands may be obtained using a larger microphone array, but beam patterns become omni-directional when a smaller microphone array is used. However, side lobes or grating lobes occur in conjunction with higher frequency bands when a larger microphone array is used. As a result, sound in an unwanted direction is acquired.
A conventional microphone array uses at least ten microphones to form a desired beam pattern. However, this increases the cost of manufacturing the microphone array and the application of acoustic signal processing of the microphone array.